Molar Vol of a Gas Lab by zhangyun

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									                                CP Chemistry
                         Molar Volume of a Gas Lab

PURPOSE: Use the ideal gas law to calculate the actual yield in moles of
a gas in a chemical reaction and the percent yield from the theoretical
yield.

MATERIALS:
gas collecting tube       thermometer                magnesium ribbon
1-hole stopper            10mL syringe               6M HCl
100mL beaker              copper wire
1L cylinder               metric ruler

PROCEDURE:

1.   Fill a 100mL beaker with tap water and allow to come to room
     temperature.

2.   From your teacher obtain and record both current room temperature
     (°C) and atmospheric pressure (mmHg).

3.   Obtain a piece of magnesium ribbon from your teacher and measure and
     record its length to the nearest .1 cm. Record the mass (provided by
     the teacher) of one meter of magnesium ribbon.

4.   Carefully fold the magnesium ribbon into a ball small enough to fit
     into the mouth of the gas collecting tube. Use the copper wire to
     enclose the magnesium in a small cage, leaving 3-4 cm of wire.

5.   Measure and record the temperature of the tap water in the 100mL
     beaker.

6.   Fill a 1L cylinder to within 2 or 3 centimeters of the top.

7.   Use the syringe to place 10 mL of 6M HCl into the gas collecting
     tube. While holding the gas collecting tube at a 45° angle,
     delicately pour the room temperature tap water into the gas
     collecting tube so that it lithely slides down the side of the tube
     and comes to rest on top of the HCl, without mixing with the HCL.
     (Since the density of the acid is greater than that of the water, the
     water will tend to float on top of the acid for a brief period of
     time.) Fill the tube all the way to the top.

8.   With the tube completely full of water, insert the ball of Mg ribbon
     attached to the copper wire about 3 or 4 cm into the tube. While
     holding the magnesium on the wire against the side of the tube,
     insert the stopper so that it forces all of the excess water and air
     bubbles out of the tube. Let the excess water & air squeeze out of
     the hole in the rubber stopper as you insert it.
9.    With your finger over the hole in the stopper and another person
      securely holding the cylinder, invert the gas collecting tube and
      place the stoppered end into the cylinder of water.

10.   Once the stopper is under the water, remove your finger and hold the
      tubein the water throughout the reaction. The reaction will begin
      when the heavier acid diffuses to the bottom of the tube and contacts
      the Mg ribbon.

11.   When the reaction is completed (no more bubbling), tap the side of
      the gas collecting tube so that all of the bubbles rise to the top.

12.   Position the gas collecting tube so that its water level exactly
      matches the water level of the cylinder. When both levels match, the
      pressure of the gas in the gas collecting is equal to atmospheric
      pressure. While holding the tube in this position, read and record
      the exact volume of the hydrogen gas.

13.   Rinse the gas tube cylinder and beaker thoroughly.

CALCULATIONS:(Show the following calculations)

1.    Write the balanced equation for the reaction of Mg with HCL to
      produce hydrogen gas.

2.    Calculate the mass of magnesium used.

3.    Using your balanced equation and the calculated mass of the
      magnesium, calculate and record the theoretical yield of hydrogen gas
      in moles.

4.    Using the ideal gas law calculate and record the actual number of
      moles of hydrogen gas that were produced.

5.    Using the theoretical yield and the actual yield, calculate and
      record the % yield.

								
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